1. Field of the Invention
The present invention relates to a yieldable joint between two elements such that the adjacent lapped edges of the elements will shift relative to each other, and more particularly to a yieldable joint which bolts together initially in correct alignment and has the ability to carry a pre-determined amount of load before any yielding can occur.
2. Description of the Prior Art
Yieldable connections which allow a lapped joint to yield under compressive load and thereby reduce the circumference of a structure so that, for example, soil may carry the load instead of the structure, and, therefore, the metal thickness of the structure may be dimished, are not new. Such connections have utilized conventional slotted holes and various other yielding devices such as sliding friction, weak bolts or compressible material. Exemplary connections are disclosed in U.S. Pat. Nos. 3,413,813, in the name of J. H. Rock, et al, 3,574,376, in the name of Wayne Cummins, and 2,645,264, in the name of Phillip Rosenberg. However, such connections have had a number of major short comings, primarily because they have utilized slotted holes and the yielding of the connections has depended upon bolt tightness and the friction between the plates to prevent premature yield of the joints. These factors are very difficult to control and highly variable. Accordingly, it has been difficult to safely design structures incorporating such connections to carry a substantial and practical overfill or pressure before any circumferential yielding occurs.